Pipelines which carry fluids are susceptible to deterioration, corrosion and other conditions which seriously affect the lifespan of the pipe. Excavation of a pipeline or pipe, to replace sections that have deteriorated, is costly and often detrimental to the environment.
In-situ pipelines of pipe typically build corrosion and scale on an inner surface, over time. The buildup within the pipe bore acts as a barrier to insertion of the liner. Large pipes can be cleared using pigging techniques, however smaller diameter pipes do not lend themselves to this type of cleaning technique. U.S. Pat. No. 4,827,553 to Turpin Sr. et al teaches passing a pipeline scraper into the bore of a pipeline and reciprocating the scraper back and forth on lengths of cable to remove residue from the bore of the pipeline.
It is known to excavate down to a portion of the pipeline from surface, sufficient to gain access to the bore of the pipe, and insert a plastic liner into the bore of the existing, in-situ pipe to prevent leakage as a result of deterioration. Typically, liner is pulled through an existing pipe at the end of a threaded cable or the like, previously installed with conventional steel rods.
Due to the unwieldy lengths of liner that are required, the supply of liner is provided at surface and must be fed into the excavation down into the bore of the pipe. Due to the angle of the minimal excavation and the usual horizontal plane of the in-situ pipe, the orientation and insertion of inflexible liners presents a challenge.
As taught in U.S. Pat. No. 4,504,171 to Florence Jr., conventional malleable liners for underground pipes are often thick and relatively stiff. In order to insert the liner into the pipe, from a point above the pipeline, the liner must first be plastically deformed, using an installation tool comprising deforming rollers, to provide a distal curve in the liner. The liner is also deformed to form a proximal curve to direct the liner downward into the excavation, while the distal curve directs the liner generally toward the pipeline. The deforming rollers are also used as drive rollers to advance the liner into the pipe.
It is known to use a roller assembly coupled directly to an old pipe and aligned in co-linear arrangement thereto so as to insert flexible plastic pipe straight into a pipe, such as that disclosed in U.S. Pat. No. 4,300,276 to Davis. Lower rollers having an annular groove and a gripping surface, such as rubber, act to guide and support a flexible pipe. The lower rollers are connected in driving relation to each other by a drive chain. Upper rubber rollers, having an annular groove, engage the upper surface of the pipe opposite the lower rollers. The rollers are arranged in-line with the pipe to avoid bending of the flexible liner. The apparatus must be placed into close proximity with the pipe to be lined, including in an excavation around the pipe itself. Also, U.S. Pat. No. 3,546,890 to Ede teaches use of an apparatus lowered into an excavation adjacent an opening and comprising three rows of motor-driven rollers having pneumatic tires as thrusting means to advance a steel pipe into the opening formed by a mole plough.
More recent development of spoolable, elongated flexible liners, such as continuous composite line pipe, (FIBERSPAR® LinePipe™ from Fiberspar Corporation, West Wareham, Mass., USA) has provided an alternative to the more inflexible varieties of liner. Particularly when a large axial force is required to advance the liner, difficulties in handling are increased due to the flexibility of this type of liner—it is difficult to push a rope. Further, the composite nature of the liner does not permit overly rough handling.
Applicant previously introduced a pusher system, as shown in published Canadian Application 2,452,413 published Mar. 5, 2005, that implements a two or more pairs of contra-rotating and pneumatic drive wheels for driving pipe therebetween. While suited for many applications and installation of composite pipe, the maximum driving force is limited and the wheeled drive interface can impose high loads on the liner.
Further, where the material properties of the pipe are less robust, there is a need for a system for inserting pipe which does not introduce excessive loads into the pipe.